1. Field of the Invention
The present invention is directed to a hydrodynamic clutch device, particularly a torque converter or fluid clutch, comprising a housing arrangement, a turbine wheel provided in the housing arrangement, a lockup clutch arrangement by means of which a torque transmission connection can be produced selectively between the turbine wheel and the housing arrangement, the lockup clutch arrangement comprising at least one substantially annular friction element which is connected to the turbine wheel for rotating jointly about an axis of rotation and a pressing element which is connected to the housing arrangement for rotating jointly about the axis of rotation and by means of which the at least one friction element can be acted upon to produce the torque transmission connection between turbine wheel and housing arrangement.
2. Description of the Related Art
In hydrodynamic clutch devices of the type mentioned above, particularly in a state in which at least some of the torque to be transmitted along an output powertrain is conducted from the housing arrangement to the turbine wheel via the lockup clutch arrangement, torsional vibrations occurring in the drive system can be contained in that a certain slip is permitted in the lockup clutch arrangement, so that torque peaks can lead to a relative rotation between the housing arrangement and the turbine wheel. This results in a comparatively large load on the structural component parts or surface regions coming into frictional contact with one another in the area of the lockup clutch arrangement, since the power losses which occur at least with greater torque fluctuations and which are contained by the slip are converted into heat.
In order to meet the demands of increasing possible power losses in the area of the lockup clutch arrangement, systems are known like those, for example, disclosed in WO 00/03158. In the hydrodynamic torque converter known from this reference, the lockup clutch arrangement has two friction elements coupled with the turbine wheel such that they rotate jointly, an intermediate friction element which is coupled with the housing arrangement for joint rotation being positioned therebetween. The individual friction surface regions are made to interact with each other by the clutch pistons acting as pressing element. By providing a plurality of radially offset friction surface pairs which can be made to interact with one another, the entire available friction surface can be appreciably enlarged without a substantial space requirement with the result that the power loss occurring in slip operation is also distributed over a larger surface and can accordingly be carried off in an improved, faster manner.
It is the object of the present invention to further develop a hydrodynamic clutch device of the type mentioned in the beginning in such a way that it has improved performance with respect to the demands arising during operation, particularly the demands occurring in slip operation.
According to the invention, a ratio of a flow outer diameter in the area of the turbine wheel to a friction outer diameter of the at least one friction element ranges between 1.30 and 1.80, preferably between 1.35 and 1.70, and/or a ratio of a friction outer diameter of the at least one friction element to a friction inner diameter of the at least one friction element ranges between 1.10 and 1.25, preferably between 1.15 and 1.20.
By means of the first step according to the invention, namely, preparing a determined ratio between the flow outer diameter and the friction outer diameter of the at least one friction element, an appreciably more favorable distribution of mass is obtained, which results in a lower mass moment of inertia. The second step according to the invention leads to a lockup clutch arrangement with larger friction surface regions, so that the occurring power losses can be better absorbed and transmitted to surrounding components or component groups.
It is preferably provided in the hydrodynamic clutch device according to the invention that, in an area radially outside of the lockup clutch arrangement, the housing arrangement has a shape that is adapted to the outer circumferential contour of the lockup clutch arrangement and to the outer circumferential contour of the turbine wheel. As a result of this step, the housing arrangement has greater rigidity particularly in its area which is also provided for the lockup clutch arrangement and for the action of the latter. This causes an appreciably smaller bulging or inflation of the converter housing under the fluid pressure prevailing in the interior of the converter housing, so that even relatively wide friction surface regionsxe2x80x94measured in radial directionxe2x80x94can not lead to edge loading of friction linings or the like induced by bulging. For example, it can be provided for this purpose that the housing arrangement is constructed in a first housing portion so as to surround the lockup clutch arrangement substantially cylindrically and has, in a second housing portion adjoining the first housing portion, a shape which is curved in direction of the axis of rotation and extends along the outer circumferential area of the turbine wheel.
According to another advantageous aspect of the present invention, it can be provided that the at least one friction element is connected to the turbine wheel so as to be essentially rigid against rotation by a driving element. Therefore, it is no longer necessary to couple the at least one friction element to the turbine wheel via a torsional vibration damper or the like with the result that the installation space can be used more efficiently and, in particular, the shape of the housing arrangement mentioned above can be provided in a simple manner.
The efficient use of construction space can be further assisted in the hydrodynamic clutch device according to the invention in that the pressing element is connected to the housing arrangement so as to rotate jointly by a driving arrangement which is arranged essentially in the axial area between the pressing element and the turbine wheel.
As was already stated, it is advantageous for increasing the effective friction surface region when a plurality of friction elements are provided, wherein an intermediate friction element connected to the housing arrangement for joint rotation is arranged between two friction elements in each instance.
In order to further optimize the mass moment of inertia existing in the hydrodynamic clutch device according to the invention, a substantially annular first coupling element can be provided which is connected in its radial inner area to an outer side of the housing arrangement, preferably by laser welding, and is constructed in its radial outer area for coupling with a second coupling element which is fixedly connected or connectable to a drive shaft.
A construction of a hydrodynamic clutch device which is particularly simple to realize and which operates on the principle of a dual-line system can be achieved in that an interior space of the housing arrangement is divided by a pressing element into a first space in which the turbine wheel is arranged and a second space, and in that work fluid can be introduced into the first space and work fluid can be conducted out of the second space, or vice versa, for an exchange of work fluid that is provided in the interior. In order to enable an exchange of fluid in a system of the type mentioned above also during the locked up state, it is proposed that at least one fluid through-opening is provided in the pressing element to enable an exchange of fluid between the first space and the second space. Further, to enable a fluid cooling in the slip state, it is further suggested that a flow channel arrangement which is preferably arc-shaped is provided in a friction surface region of the at least one friction element. This flow channel arrangement is then preferably open toward the two spaces, so that a passage of fluid through the flow channel arrangement will take place due to the pressure difference between the two spaces which exists in any case in the locked up state, and the heat energy occurring in this spatial region can be carried off.